Datamodeling Assistant issue (computing incorrectly a null value)

[ale_g]

Hi all.
I have Genesys 6.5 running under windows.
After creating a custom filter on the Data modeling Assistant application to filter some calls (using the function 'PairExist("TipoServicio","TEC")' I found out that calls not having at all the variable "TipoServicio" defined are being filtered in.

Do you know the reason for this strange behavior? (All calls that do have the variable "TipoServicio" attached are being computed fine.

B. Regards
Alejandro